Irinotecan and Capecitabine in Treating Patients With Solid Tumors

DISEASE CHARACTERISTICS: Histologically confirmed solid tumors, including but not limited to breast, gastrointestinal, and unknown primary cancer that is refractory to standard therapy or for which no standard therapy exists No known bone marrow involvement PATIENT CHARACTERISTICS: Age: 18 and over Performance status: Karnofsky 60-100% Life expectancy: Not specified Hematopoietic: Absolute neutrophil count at least 1,500/mm3 OR WBC at least 3,500/mm3 AND Platelet count at least 100,000/mm3 Hepatic: Bilirubin no greater than 1.5 mg/dL No known Gilbert's syndrome No other significant hepatic disease requiring medication Renal: Creatinine no greater than 1.5 mg/dL Cardiovascular: No significant cardiac disease requiring medication Other: Not pregnant or nursing Fertile patients must use effective contraception No other significant medical condition PRIOR CONCURRENT THERAPY: Biologic therapy: At least 2 weeks since prior colony stimulating factor and other cytokines active on bone marrow Chemotherapy: At least 4 weeks since prior chemotherapy (6 weeks since mitomycin or nitrosoureas) No prior or concurrent irinotecan and fluorouracil therapy Endocrine therapy: Not specified Radiotherapy: At least 4 weeks since prior radiotherapy No concurrent radiotherapy Surgery: Recovered from prior major surgery